REGULATION OF BENIGN AND MALIGNANT HEPATOCYTE GROWTH

描述（由申请人提供）：肝细胞癌（HCC）除了是全球癌症死亡的主要原因之一外，每年还导致超过35,000名美国人死亡。手术切除是肝细胞癌患者的最佳治疗方法，但只有20-40%的确诊患者可行。由于我们缺乏对HCC的细胞和分子水平的病因学的了解，因此未能开发出肝癌的替代疗法。我们实验室之前的报告已经确定了丝裂原活化蛋白激酶（MAPK）级联的成分是处理各种来源信号的焦点，包括与鸟嘌呤核苷酸调节蛋白（c蛋白）偶联和酪氨酸激酶连接受体相关的信号。具体来说，我们已经证明在80%以上的人类HCC中抑制g蛋白（giprotein）的表达和功能发生了改变。此外，在人类和动物HCC模型中，gi蛋白的激活通过丝裂原激活蛋白激酶（MAPK）级联导致丝裂发生增强，这一效应在未转化的肝细胞中未观察到。我们实验室的其他数据表明，在肝癌和非致瘤性、组织学上正常的肿瘤动物肝脏组织中，肝脏胰岛素样生长因子- 1 （igf - 1）的表达发生了变化。用igf - 1刺激HCC细胞通过MAPK途径导致细胞有丝分裂增加，这一作用被抑制gi蛋白信号通路所消除。基于这些观察结果，本提案的中心假设是MAPK级联代表了不同来源的跨膜信号之间的焦点联系，其调节直接影响多个水平的肝肿瘤增殖，并与HCC细胞有丝分裂特征的增加具有内在联系。NIH-R01一等奖的目的是“确定MAPK成分在膜、细胞质和核水平上调节细胞有丝分裂的机制”。具体来说，我们将(i)与刺激或抑制这些信号通路的特定药理学制剂一起，过表达g蛋白/IGF-l-MAPK信号通路的构成性活性或显性阴性成分。这些数据将确定c蛋白亚基和tk连接受体及其相关的第二信使在HCC中调节细胞质（MAPK）信号通路中的作用。（ii）确定g蛋白/IGF-l-MAPK通路在正常和转化（HCC）肝细胞中调节核转录因子和细胞增殖和存活中的作用。由于与HCC相关的死亡率如此之高，破译细胞生长和肿瘤进展发生的机制显然具有重要的临床重要性和意义。因此，在细胞质和细胞核水平上阐明控制细胞增殖的机制代表了不可切除HCC新治疗方法发展的潜在突破。

DESCRIPTION (provided by applicant): Hepatocellular cancer (HCC) leads to the death of more than 35,000 Americans annually in addition to being one of the leading causes of cancer death worldwide. Surgical resection is the best treatment available to patients with HCC but is a viable option for only 20-40% of those diagnosed. The failure to develop alternative treatments for HCC is due to our lack of understanding of the disease etiology at the cellular and molecular level. Previous reports from our laboratory have identified components of a mitogen activated protein kinase (MAPK) cascades as a focal point in processing signals of diverse origin including those associated with guanine nucleotide regulatory protein (C-protein) coupled and tyrosine kinase-linked receptors. Specifically, we have demonstrated altered expression and function of inhibitory G-proteins (Giproteins) in more than 80% of human HCC analyzed. Furthermore, activation of Gi-proteins in human and animal models of HCC leads to enhanced mitogenesis via a mitogen activated protein kinase (MAPK) cascade, an effect not observed in non-transformed hepatocytes. Other data from our laboratory demonstrate changes in hepatic insulin-like growth factor-I (IGF-l) expression in HCC and non-tumorigenic, histologically normal hepatic tissue in tumor burdened animals. Stimulation of HCC cells with IGF-l leads to increased cell mitogenesis via a MAPK pathway, an effect abrogated by inhibition of Gi-protein signaling.Based on these observations the central hypothesis of this proposal is that a MAPK cascade represents a focal link between transmembrane signals of diverse origin, regulation of which directly affects hepatic tumor proliferation at multiple levels and is intrinsically linked to the increased cell mitogenesis characteristic of HCC. It is the aim of this NIH-R01 First Award to "determine the mechanisms by which MAPK components regulate cell mitogenesis at the membrane, cytoplasmic and nuclear levels." Specifically we will (i) over-express constitutively active or dominant negative components of G-protein/IGF-l-MAPK signaling pathways in conjunction with specific pharmacological agents that stimulate or inhibit these pathways. These data will determine the role of C-protein subunits and TK-linked receptors and their associated second messengers in regulating cytoplasmic (MAPK) signaling pathways in HCC. (ii) determine the role of G-protein/IGF-l-MAPK pathways in regulating nuclear transcription factors and cell proliferation and survival in normal and transformed (HCC) hepatocytes.Because the mortality associated with HCC is so high, deciphering the mechanisms by which cell growth and tumor progression occurs is clearly of major clinical importance and significance. Accordingly, elucidation of the mechanisms controlling cell proliferation at the cytoplasmic and nuclear level represents a potential breakthrough in the development of new treatments for non-resectable HCC.